Protective effect of L-arginine preconditioning on ischemia and reperfusion injury associated with rat small bowel transplantation

The role of the exogenous supply of adenosine triphosphate in the expression of Bax and Bcl2L1 genes in intestinal ischemia and reperfusion in rats 1

PURPOSE

To investigate the role of the exogenous supply of adenosine triphosphate (ATP) in the expression of Bax and Bcl2L1 genes in intestinal ischemia and reperfusion (IR) in rats.

METHODS

The study was designed as a randomized controlled trial with a blinded assessment of the outcome. Eighteen adult male Wistar-EPM1 rats were housed under controlled temperature and light conditions (22-23°C, 12 h light/dark cycle). The animals were randomly divided into 3 groups: 1. Sham group (SG): no clamping of the superior mesenteric artery; 2. Ischemia and reperfusion group (IRG): 3. Ischemia and reperfusion plus ATP (IRG + ATP). ATP was injected in the femoral vein before and after ischemia. Afterwards, intestinal segments were appropriately removed and processed for Endothelial Cell Biology Rat RT2 Profiler PCR Array.

RESULTS

ATP promoted the upregulation of Bcl2L1 gene expression, whereas it did not have significant effects on Bax gene expression. In addition, the relation of Bax/Bcl2L1 gene expression in the IRG group was 1.39, whereas it was 0.43 in the IRG + ATP group. Bcl2L1 plays a crucial role in protecting against intestinal apoptosis after ischemia and reperfusion. Increased Bcl2L1 expression can inhibit apoptosis while decreased Bcl2L1 expression can trigger apoptosis.

CONCLUSION

Adenosine triphosphate was associated with antiapoptotic effects on the rat intestine ischemia and reperfusion by upregulating of Bcl2L1 gene expression.

L-Arginine Modulates Intestinal Inflammation in Rats Submitted to Mesenteric Ischemia-Reperfusion Injury

BACKGROUND

The goal of this study was to investigate whether exogenous offer of L-arginine (LARG) modulates the gene expression of intestinal dysfunction caused by ischemia and reperfusion.

METHODS

Eighteen Wistar-EPM1 male rats (250-300 g) were anesthetized and subjected to laparotomy. The superior mesenteric vessels were exposed, and the rats were randomized into 3 groups (n = 6): the control group (CG), with no superior mesenteric artery interruption; the ischemia/reperfusion group (IRG), with 60 minutes of ischemia and 120 minutes of reperfusion and saline injections; and the L-arginine group (IRG + LARG), with L-arginine injected in the femoral vein 5 minutes before ischemia, 5 minutes after reperfusion, and after 55 minutes of reperfusion. The total RNA was extracted and purified from samples of the small intestine. The concentration of each total RNA sample was determined by using spectrophotometry. The first-strand complementary DNA (cDNA) was synthesized in equal amounts of cDNA and the Master Mix SYBR Green qPCR Mastermix (SABiosciences, a Qiagen Company, Frederick, Md). Amounts of cDNA and Master Mix SYBR Green qPCR Mastermix were distributed to each well of the polymerase chain reaction microarray plate containing the predispensed gene-specific primer sets for Bax and Bcl2. Each sample was evaluated in triplicate, and the Student t test was applied to validate the homogeneity of each gene expression reaction (P < .05).

RESULTS

The gene expression of Bax in IRG (+1.48) was significantly higher than in IRG-LARG (+9.69); the expression of Bcl2L1 in IRG (+1.01) was significantly higher than IRG-LARG (+22.89).

CONCLUSIONS

The apoptotic cell pathway of 2 protagonists showed that LARG improves the gene expression of anti-apoptotic Bcl2l1 (Bcl2-like 1) more than the pro-apoptotic Bax (Bcl2-associated X protein).

Effects of oral administration of (L)-arginine, (L)-NAME and allopurinol on intestinal ischemia/reperfusion injury in rats

AIMS

Intestinal ischemia/reperfusion (I/R) injury is implicated in many clinical conditions, and it performs a fundamental role in their pathophysiologies. Oral administration of antioxidants and nitric oxide (NO) donors ameliorate intestinal injury. Here, the effects of l-arginine, allopurinol and N(G)-nitro-l-arginine methyl ester (l-NAME) were investigated.

MAIN METHODS

One hundred twenty-eight male Wistar rats were separated into 4 groups and subjected to occlusion of the superior mesenteric artery for 60 min. The Control group did not receive any substance before the surgical operation. However, the 3 other groups received the following: l-arginine (800 mg/kg body weight; l-Arg group), l-NAME (50mg/kg; l-NAME group) or allopurinol (100mg/kg; Allo group). Each substance was given by mouth in 3 equal doses 24, 12 and 1h before the surgical operation. Each group was then divided into 4 subgroups, which underwent different durations of reperfusion (0, 1, 8 or 24h). At the end of each time point, blood and tissue samples were collected, and histological examinations were performed. Serum nitrite and catalase, intestinal tissue myeloperoxidase (MPO), inducible nitric oxide synthase (iNOS) and nitrotyrosine (NT) levels were determined.

KEY FINDINGS

At each reperfusion time point, the Allo group exhibited the mildest histological lesions in contrast to the l-NAME group, which showed the most severe lesions. MPO was decreased significantly in the Allo and l-Arg groups during reperfusion, and allopurinol administration caused earlier and stronger effect. iNOS and NT levels were higher in the l-Arg group and lower in the Allo group. Serum nitrite and catalase were increased in the l-NAME group after 24h.

SIGNIFICANCE

Oral administration of allopurinol exerted a strong and protective effect on the intestinal tissue that was subjected to I/R earlier than l-arginine. This finding was also supported with the MPO, iNOS and NT data.

Different ischemic preconditioning regimens affecting preservation injury of intestines

Decreasing ischemia-reperfusion injury in intestinal transplantation is of paramount importance for improving graft recovery and function. This study explores the ability of two ischemic preconditioning (IPC) regimens to reduce preservation injury. Sprague-Dawley rats were divided into 3 groups (n = 11 each). In the controls (group C), intestinal grafts were harvested and preserved. IPC was performed either through 4 cycles of mesenteric ischemia of 4 min each followed by 10 min of reperfusion (group BIPC) or 2 ischemic cycles of 12 min each followed by 10 min of reperfusion (group LIPC). Grafts were stored in histidine-tryptophan-ketoglutarate, and samples were taken 0, 3, 6, 9, 12, 18, and 24 h after preservation. Preservation injury was scored using the Park/Chiu scale. Goblet cells (GC), enteroendocrine cells (EEC) and serotonin-producing EEC (SPEEC) were studied for evaluation of the graft conditions. Group C had the most advanced preservation injury followed by group BIPC. GC count was lowest in group C, followed by BIPC. Comparison between groups BIPC and LIPC showed superior parameters (preservation injury, GC, EEC, and SPEEC) in LIPC. In conclusion, an IPC regimen of 2 ischemic cycles of 12 min each followed by 10 min of reperfusion distinctly decreased the preservation injury of intestinal grafts compared with non-manipulated grafts.

Proteomic analysis of intestinal ischemia/reperfusion injury and ischemic preconditioning in rats reveals the protective role of aldose reductase

Intestinal ischemia/reperfusion (I/R) injury is a critical condition associated with high morbidity and mortality. Studies show that ischemic preconditioning (IPC) can protect the intestine from I/R injury. However, the underlying molecular mechanisms of this event have not been fully elucidated. In the present study, 2-DE combined with MALDI-MS was employed to analyze intestinal mucosa proteomes of rat subjected to I/R injury in the absence or presence of IPC pretreatment. The protein content of 16 proteins in the intestinal mucosa changed more than 1.5-fold following intestinal I/R. These proteins were, respectively, involved in the cellular processes of energy metabolism, anti-oxidation and anti-apoptosis. One of these proteins, aldose reductase (AR), removes reactive oxygen species. In support of the 2-DE results, the mRNA and protein expressions of AR were significantly downregulated upon I/R injury and enhanced by IPC as confirmed by RT-PCR and western blot analysis. Further study showed that AR-selective inhibitor epalrestat totally turned over the protective effect of IPC, indicating that IPC confers protection against intestinal I/R injury primarily by increasing intestinal AR expression. The finding that AR may play a key in intestinal ischemic protection might offer evidences to foster the development of new therapies against intestinal I/R injury.

Pulmonary perfusion with L-arginine ameliorates post-cardiopulmonary bypass lung injury in a rabbit model

BACKGROUND

Post-cardiopulmonary bypass (CPB) lung injury is the combination of whole body inflammatory response and local ischemia-reperfusion (IR) injury. We investigated the benefit of pulmonary perfusion with L-arginine in protection against post-CPB lung injury.

METHODS

New Zealand white rabbits (n = 50, weight, 2.5-2.8 kg) were divided into five groups (n = 10 each): sham (sham sternotomy), CPB (CPB without pulmonary perfusion), perfusion (CPB with pulmonary perfusion), L-arginine (CPB with perfusion + L-arginine), and L-NAME (CPB with perfusion + L-NAME). The duration of CPB was 60 min followed by 2 h of reperfusion. Pulmonary perfusion was performed every 20 min through the pulmonary artery during CPB. Checking parameters included: (1) pulmonary vascular resistance, (2) pulmonary artery endothelium relaxation (organ chamber study), and (3) IR marker (myeloperoxidase) and inflammatory markers (TNF-α, IL-B, NF-κB).

RESULTS

CPB induced pulmonary artery endothelium dysfunction manifested by increased pulmonary vascular resistance and impaired pulmonary artery relaxation. Pulmonary perfusion could significantly reverse the phenomenon (P < 0.01) while provision of NO precursor-L-arginine with pulmonary perfusion together further possessed significant relaxation ability for pulmonary arterial endothelium compared with perfusion alone (P < 0.05). Accordingly, lung parenchyma myeloperoxidase activity and inflammatory cytokine level were also markedly increased after CPB (P < 0.05). Pulmonary perfusion could partially decrease the response, whereas additional L-arginine further attenuated inflammatory cytokine release (P < 0.05).

CONCLUSIONS

Pulmonary perfusion during CPB partially ameliorates CPB-induced lung injury. Pulmonary perfusion with L-arginine could further attenuate lung injury by restoring endothelial function and decreasing inflammatory response.

Evaluation of a Novel Cold Storage Solution (HBS) in a Rat Kidney Transplant Model

We developed an improved solution for hypothermic storage (0-4 degrees C) of kidneys. The cold storage solution (HBS) was composed of macromolecules, high-energy cellular substrates, and a mixture of antiproteolytic amino acids, antioxidants, and anti-inflammatory compounds. The objectives in developing this solution were to achieve superior metabolic support of the kidney during cold storage and to protect against ischemic injury. Inbred Brown Norway rats, weighing 225-250 g, were subjected to orthotopic ultrarapid technique for kidney isotransplantation to minimize warm ischemia and to test the preservation process. The kidney was transplanted after 12 h of preservation. The animals were divided into three groups based upon the preservation solution utilized: HBS solution, HTK solution (Custodiol), and UW solution (UWS)(ViaSpan). Among the recipients, each group had two subsets. The first subset of animals was used to assess survival at 7 days as well as the reperfusion damage index (RDI) based on the macroscopic physical characteristics of the kidney at the time of transplantation. The second subset in each group was utilized to measure serum creatinine and blood urea nitrogen at 4 and 7 days, and histology at death or sacrifice. Mean +/- standard deviation (M +/- SD) was used for all parameters studied. The HBS solution showed significantly better protection at 12 h when compared to HTK and UW solutions. The reperfusion damage index (RDI) showed excellent preservation in the HBS (14 +/- 1), good preservation in UWS (13 +/- 1.5), and moderate preservation in the HTK (11 +/- 2) group. Histology was in concordance with the RDI, showing better histological findings with HBS and UW solutions than with the HTK group. Serum creatinine was significantly better in the HBS group when compared to HTK and UWS. Survival was statistically different, with 80% survival at 7 days in the HBS group, 20% survival in the HTK group, and 50% survival in the UWS group (p < .05). The HBS solution offered a new alternative for kidney cold storage with significantly better results when compared to the current gold standards of HTK and UW solutions in Brown Norway rats. This solution warrants further testing in other mammals.

Protective effect of arginine on oxidative stress in transgenic sickle mouse models

Sickle cell disease (SCD) is characterized by reperfusion injury and chronic oxidative stress. Oxidative stress and hemolysis in SCD result in inactivation of nitric oxide (NO) and depleted arginine levels. We hypothesized that augmenting NO production by arginine supplementation will reduce oxidative stress in SCD. To this end, we measured the effect of arginine (5% in mouse chow) on NO metabolites (NOx), lipid peroxidation (LPO), and selected antioxidants in transgenic sickle mouse models. Untreated transgenic sickle (NY1DD) mice (expressing approximately 75% beta(S)-globin of all beta-globins; mild pathology) and knockout sickle (BERK) mice (expressing exclusively hemoglobin S; severe pathology) showed reduced NOx levels and significant increases in the liver LPO compared with C57BL mice, with BERK mice showing maximal LPO increase in accordance with the disease severity. This was accompanied by reduced activity of antioxidants (glutathione, total superoxide dismutase, catalase, and glutathione peroxidase). However, GSH levels in BERK were higher than in NY1DD mice, indicating a protective response to greater oxidative stress. Importantly, dietary arginine significantly increased NOx levels, reduced LPO, and increased antioxidants in both sickle mouse models. In contrast, nitro-L-arginine methylester, a potent nonselective NOS inhibitor, worsened the oxidative stress in NY1DD mice. Thus, the attenuating effect of arginine on oxidative stress in SCD mice suggests its potential application in the management of this disease.